Various types of hair extension devices are known in the prior art. However, what has been needed is a hair extension sewing device including a base, an opening, a needle, a hook, a pair of curved hook extenders, a pair of grips, a thumb controller, an activation control, and a motor. What has further been needed is for the thumb controller to have a selectively activated position. The thumb controller is in the activated position when a user applies a downward pressure to the thumb controller. Lastly, what has been needed is for the hook to be configured to create a loop in a thread when the thumb controller is in the activated position. The needle is also configured to stitch the thread through a hair extension when the thumb controller is in the activated position. The hair extension sewing device enables a user to avoid the time and effort that is required to sew in a hair extension by hand. Instead, a user can now quickly and efficiently utilize the hair extension sewing device to sew in hair extensions at home or in a salon.